In cross-country or tour skiing, one aspect which is of considerable importance is the running surface of the ski, because such surface must be designed to reduce friction while gliding and yet provide sufficient control and stability with respect to kicking and climbing. Traditionally, tour-ski running surfaces, which engage the snow or ice, have had to be waxed carefully. A known alternative has been to modify structurally the running surface. Early attempts to modify such a surface were disclosed in U.S. Pat. No. 3,381,972. An improvement on this teaching was the utilization of a three-dimensional scale formation on the running surface, as exemplified in U.S. Pat. No. 3,408,086, hereby incorporated by reference. This patent discloses the employment of rows of protuberances with convexly curved edges along the running surface in a regular, repeating pattern over the gliding surface of the ski. Additionally, U.S. Pat. No. 3,858,894, hereby incorporated by reference, should be noted as an improvement on U.S. Pat. No. 3,408,086 in which protuberances, particularly trapezoidaltype formations, are nonharmonically spaced to eliminate or reduce the noise level during gliding movement of the ski.
While these variations of protuberances have been known for some time, they, alone, have not satisfied fully the combined requirements of skiers as to reducing friction while gliding, yet providing sufficient snow-gripping action during climbing and kicking maneuvers.